sysutils/scanbd: Add new port

scanbd looks to be the continuation of scanbuttond, it accomplishes
the same tasks, but supports all scanners from scanbuttond plus all
the scanners supported by SANE. It uses dbus for communication and can
also signal device insertion and removal.

Upstream has moved to gitlab, so this is the last corresponding release
based on the last SourceForge release (with some minor documentation
updates).

WWW: https://sourceforge.net/projects/scanbd/

PR: 271816